— Gregor MendelContext: Of the experiments of previous years, those dealing with Matthiola annua and glabra, Zea, and Mirabilis were concluded last year. Their hybrids behave exactly like those of Pisum. Darwin's statements concerning hybrids of the genera mentioned in The variation of animals and plants under domestication, based on reports of others, need to be corrected in many respects.
Letter VIII, July 3rd, 1870.
Here Mendel alludes to the now-discredit ideas of blending inheritance and pangenesis

— Gregor MendelContext: Experience of artificial fertilisation, such as is effected with ornamental plants in order to obtain new variations in colour, has led to the experiments which will here be discussed. The striking-regularity with which the same hybrid forms always reappeared whenever fertilisation took place between the same species induced further experiments to be undertaken, the object of which was to follow up the developments of the hybrids in their progeny.
Introductory paragraph